There is not a whole lot to learn to use telnet. If you have a UNIX system at hand, just type "man telnet" and you will have plenty of details. Basically, telnet is a remote (interactive) access client-server application protocol that allows you to interact with a remote host/server. The man page will give details.

-l <user> connects to the machine with a special username
-n <file> makes a file that traces your telnetsession

all other options like -c -d -8 -e -E -L -n i normaly don`t use, but you can read at the man-page section ("man telnet").

example:

you wanna connect to host "hugoland" as user "hugo", but you are user "root" on your machine. type:

telnet -l hugo hugoland

there is another interresting thing to know: normaly telnet connects automatic to port 23. this is defautl-tcp/ip standard. but when you wanna connect to another port (like 2031) type

telnet -l hugo hugoland 2031

this is the "client side" of telnet. now some words about the "server side".

if you wanna have a machine (server) to allow someone connect to your server per tlent, you have to run a telnet-daemon. this examples are from sun solaris 8, but normaly it`s nearly the same on hp-ux and aix.

the telnet server is controled by the "master-process" of all net-services "inetd". in the /etc/inetd.conf there are entrys for all services the "inetd" habe to serv/control. when you wanna enable/disable the telnet-service (from serverside!) comment/uncomment the line in the /etc/inetd.conf and restart the "inetd" (kill -1 <proc-id od inetd>)

on secury systems root is denied to login per telnet or ftp. this is defined in the /etc/default/login (on sun solaris) and/or in the /etc/ftpusers.